Fluorescence in situ hybridization (FISH) assays are increasingly used to identify chromosomal translocations, duplications, deletions, and other chromosomal abnormalities associated with specific cancers. However, current assay formats rely on manual and labor intensive microscopic examination making rare cell detection impractical. For early diagnosis of leukemias and for detecting therapeutic relapse, sensitive, high throughput assays which can detect one cancer cell in the presence of at least 1,000 non-cancerous cells are needed. By combining gel microdrop single cell encapsulation (GMD) technology, fluorescence in situ hybridization (FISH), and flow cytometry, we have developed an assay to detect telomerase mRNA (tmRNA), which is a potentially valuable marker for early cancer detection because carcinogenesis is dependent on telomerase activation. Using clinical samples, Phase I research will identify cancer cells in human blood for early diagnosis of chronic leukemias. PROPOSED COMMERCIAL APPLICATIONS: The assay will permit early and accurate diagnosis of cancer, facilitating early treatment and reducing mortality rates. The assay will also permit monitoring of the effectiveness of the clinical treatment, facilitating development of new therapeutics and cancer treatments.